Different moorland plants, particularly heather and cotton grass, can strongly influence climate warming effects on greenhouse gas emissions, according to the study. The findings show that valuable carbon stores, which lie below peaty moorlands, are at risk from changes in climate and from land management techniques that alter plant diversity.

The NERC-funded study was led by Dr Sue Ward (University of Lancaster) with colleagues from the University of Manchester and the Centre for Ecology & Hydrology. They used long-term ECN climate records for the site.

The team installed open-topped glass chambers on moorland vegetation to increase temperatures by about 1°C. Within the chambers, the composition of vegetation was altered by selectively removing some species. During the course of the study, the team measured fluxes of greenhouse gases such as carbon dioxide and methane, levels of dissolved organic carbon in water, soil nutrients and rates of decomposition.

The researchers found that when heather was present, warming increased the amount of CO2 taken up from the atmosphere, making the ecosystem a greater sink for this greenhouse gas. However, when cotton grass was present, the CO2 sink strength of the system decreased with warming, and the amount of methane released increased.

The fact that the diversity and make-up of the vegetation completely changed the sink strength of the ecosystem for carbon dioxide came as a surprise to the scientists. It means that the way peatland vegetation is managed will strongly influence the way that peatland carbon sink strength responds to future climate change. The research has implications for peatland farming and conservation.